Diamond and Related Materials 11 (2002) 1295–1299 0925-9635/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-9635 Ž 01 . 00549-0 X-Ray absorption study of the bonding structure of BCN compounds enriched in carbon by CH ion assistance 4 R. Gago , I. Jimenez *, U. Kreissig , J.M. Albella a,c a,b, c a ´ Instituto de Ciencia de Materiales de Madrid (C.S.I.C.), Cantoblanco, 28049 Madrid, Spain a Instituto de Ciencia y Tecnologıa de Polımeros (C.S.I.C.), Juan de la Cierva 3, 28006 Madrid, Spain b ´ ´ Institut fur Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf e.V., PF 510119, D-01313 Dresden, Germany c ¨ Abstract Ternary BCN compounds can be grown by B C evaporation and concurrent N yAr ion assistance in both hexagonal and cubic 4 2 structures, depending on the deposition parameters. However, the films are always carbon poor, with a maximum carbon content of approximately 10 at.% in hexagonal BCN, and 5 at.% of C in cubic BCN. In order to increase the carbon content in the films, we have added CH to the bombarding gas mixture. In the case of hexagonal structures, the additional carbon atoms are efficiently 4 incorporated to the h-BCN without finding a solubility limit. For the cubic structures, the carbon enrichment induces a disruption of the structure and segregation into h-BCN and B C domains.  2002 Elsevier Science B.V. All rights reserved. x Keywords: Nitrides; Carbides; Ternary BCN; X-Ray absorption near edge spectroscopy 1. Introduction BCN compounds are interesting in both the cubic (c- BCN) and hexagonal (h-BCN) structure. On the one hand, the synthesis of c-BCN is aimed at the production of super-hard materials w1,2x since properties between those of cubic boron nitride (c-BN) and diamond would be obtained w3x. On the other hand, h-BCN have potential applications in microelectronics w4x, since they are expected to behave as semiconductors of varying gaps depending on the composition and atomic arrange- ment w5x, or in the production of nanotubes w6x. The synthesis of ternary BCN compounds seems possible based on the similar structure between graphite and hexagonal boron nitride (h-BN) and between dia- mond and c-BN, respectively. However, only in a few reports the production of a real ternary compound is clear since the presence of BC, BN and CN bonding is not enough to discern between a true ternary phase and a mixture of segregated binary phases. X-Ray absorption near edge spectroscopy (XANES) w7x is a suitable technique to face this problem since it is sensitive to *Corresponding author. Tel.: q34-91-334-9081; fax: q34-91-372- 0623. E-mail address: ijimenez@icmm.csic.es (I. Jimenez). ´ the individual local environments of each element pres- ent in the sample. In previous work we have reported the identification by XANES of ternary BCN compounds with either hexagonal w8x or cubic w9x structure grown by ion beam assisted evaporation. However, the carbon content found in the films was always low, with maximum carbon contents of approximately 10 at.% in hexagonal struc- tures and approximately 5 at.% in cubic structures. The question posed at this point is if the carbon limitation is an intrinsic feature due to a solubility limit or if it is a result of the deposition process. Our recent efforts have been aimed at the increase of the carbon content in BCN by adding CH to the assistance gas mixture 4 w10x. In the present work we study by XANES how the new carbon atoms are incorporated to the film and discuss the solubility limits of carbon in h-BCN and c- BCN structures. 2. Experimental 2.1. Film deposition The deposition system employed for sample prepara- tion has been described elsewhere w10x. The source of